Not only, but also some of us -including me- know by heart 32768 and 65536. Though I've yet to meet anyone who knows the output of perl -le 'print 1<<24' or perl -le 'print ~0' (32-bit machine here!) in anticipation, albeit I suspect quite more than one does. Anyone here?

Ouch! Now that I'm staring at them I fear I will learn them by heart too... ;-)

1<<24? Sure. I even used that knowledge to show off like a dork in a statistics lecture in college. The prof was doing some kind of probability calculation that led to a result of 1 in 4^12, I think, and asked someone to punch 4^12 into a calculator and tell him what it was. Of course, 4^12 is 2^24, which I happened to know by heart was 16,777,216. (Why? It's the number of possible colors on a display that allocates one byte each to the red, green, and blue channels, and it just stuck with me.)

When I rattled off that number a fraction of a second after his asking, without my calculator out, a bunch of folks in the lecture hall turned and looked at me like I was Rain Man or something. Of course, I was just lucky; I couldn't have done it if it hadn't been a reasonably common power of 2.